The original concept behind SDN (Software Defined Networking) was to create an open-source approach to networking. At a high level, centralised management servers form the basis of vendor network intelligence with end devices based on low cost, high throughput hardware which reach out to the management server for their networking configuration and security policies.

The capability across SD WAN solutions is today becoming more aligned with this vision as businesses are deploying WAN edge devices which take their configuration directly from Cloud-based management servers.

SD WAN is delivered via a process of orchestration, a provider or vendor delivers software-WAN via their platform to manage and deploy their service. This typical architecture is an SDN controller with virtualisation software which automates provisioning and operation of each cloud-based software element.

The SDN controller can be thought of as the intelligence which, in combination with each virtualized network component, provides business with their solution. A virtualised infrastructure manager (VIM), manages the network resources. By leveraging the VIM, an SDN controller can understand which connections & cloud resources are required to meet the SD WAN network services offering.

Cloud SD-WAN orchestration is the enabler to efficient customer Enterprise provisioning and deployment.

Why does your business need SD WAN?

a) Cost savings - generated by the use of Internet connectivity vs expensive private MPLS circuits. The reality is that there isn't a huge disparity between UK Internet and MPLS which often disappoints IT teams when the promise of huge cost reduction is not realised. The US SD WAN provider market is different though, MPLS cost is significantly higher vs Internet resulting in the marketing hype becoming a reality. With this said, using UK Internet as the basis of your VPN means IT teams are positioned to search for the lowest pricing per HQ or branch location. We wouldn't necessarily recommend a multi-ISP strategy but every solution requirement is different.

b) Agility - zero-touch deployment via cloud-based configuration at a moment's notice with support for multiple connectivity types including Broadband, 4G, 5G and Ethernet services all configured via a GUI based interface. Managed SD WAN is also available for deployments where additional config support is required.

c) Security - a single device often provided with next-generation Firewall and VPN Security features meaning an additional device is not required to secure your network. SD WAN meets the demands of Enterprise business by offering granular security policies which can be deployed per traffic or user type.

d) WAN optimisation & network performance - using the Internet requires intelligent QoS and path selection. Traditional private WAN offers end to end QoS with 6 typical traffic settings (EF, AF, Be with High/Low). With SD WAN, traffic sensing is applied to make decisions based on high latency, jitter or outage flags with alternative path selection as required. WAN caching and TCP acceleration round off optimisation, remember that these technologies have been available prior to SD WAN but not as a consolidated single platform.

e) Network performance analysis - reporting is a critical area of networking regardless of WAN technology. SD WAN meets the demands of traffic profiling by applying detailed analysis of traffic at the same time as presenting the data back to your IT team via easy to understand single pane of glass graphical representations. The reporting aspect is key to trend analysis, enabling the ability to predict future bandwidth and service needs.

f) Cloud IaaS, PaaS, SaaS & Storage - secure access to cloud applications due to adoption of public IP as the choice of backbone.

Will SD WAN replace MPLS?

MPLS private network WAN capability should remain a component of any good Hybrid WAN architecture. SD WAN technology is decreasing the prevalence of new large scale MPLS networks due to the feature rich nature of software-defined WAN. With this said, MPLS can be made more flexible using SD WAN technology, all of the features we know to make up the basis of SD WAN can be leveraged as an WAN edge device for MPLS provision.

How to compare each SD WAN solution vs feature-set?

We’ll cover the 16 SD WAN solution features and then proceed to look at 10 top/best selected providers and vendors in more detail. The majority of Software WAN solutions are available as wires only or with value-added services including managed SD WAN capability.

1. Year launched

The year of any SD WAN solution launch may not appear to be the most pertinent data point but experience is a significant area to consider. In some respects, certain providers & vendors may already have a track record in delivering WAN services but perhaps are new to the SD WAN space. If the technology is proprietary, a trial of real-world performance and reliability is highly recommended.

2. Which SD WAN providers feature on the Gartner Magic Quadrant?

The results of Gartners WAN edge infrastructure analysis offers an insight into how Gatner analysts perceive the capability of SD WAN solution leaders. While we respect the reporting structure, recommendations may not fully align your specific business requirements. Our experience tells us that it is critical to fully understand the true technical elements of any service offering vs your specific requirements. There are many use cases where certain providers are not fully recommended even though they may appear, on the surface, to be leading the way in respect of overall solution features.

3. What is the Providers SD WAN architecture?

Selected providers offer SD WAN solutions with access to their own IP backbone to deploy WAN connections. Others provide the intelligence but ask you to bring your own ISP connectivity. The need to consider WAN architecture in respect of software-based solutions requires some consideration.

The providers with their own infrastructure use edge PoPs within each region which interconnect with private traffic-engineered MPLS circuits. The mention of MPLS within an Internet SD WAN world often results in raised eyebrows. But, the reality is, MPLS remains a great way to send IP traffic from one location to another with predictable latency and throughput. In the service provider world, IP traffic engineering is still needed to avoid network bandwidth congestion. The take away is that, for businesses outside of network infrastructure providers, SD WAN arguably defeats the MPLS & VPLS QoS (Quality of Service) argument due to the intelligence to circumvent the lack of end to end guarantee of traffic for voice and video prioritisation. The provider PoP architecture allows HQ and branch locations to leverage national low cost ISP circuits because the hop is only to the service providers edge node. Whereas providers without WAN infrastructure will normally align with a number of Internet providers to deliver services which 'could' impact service levels - something to consider.

4. What is the solution form factor?

SD WAN is currently available across physical hardware, virtual machines, cloud-based or via white boxes (uCPE). The use of white boxes is something which will grow in the future as the true capability of SDN (Software Defined Networking) matures.

5. Where is the management controller located?

The decision of where to locate an SD WAN management controller is largely based on the solution product description. As an example, Meraki management and configuration controllers are based within a customer hosting facility (DataCentre) or with an HQ site. Outside of Meraki, the controller may be hosted by the SD WAN provider within their Cloud infrastructure. (I'm using Meraki as an example)

6. What happens if our business is disconnected from the SD WAN controller?

If your edge devices are disconnected from the management controller, potential issues occur depending on the capability of your solution. As an example, sites can continue to operate but may not receive routing updates or learn new MAC addresses. Other solutions may allow you to route via an alternative location or connections.

7. Does my SD WAN solution offer advanced next-generation Security?

SD WAN next generation security is offered as basic, stateful and advanced next-generation with anti-malware, IDS, IPS, content filtering and sandbox operation. The security policies are defined by the management interface, how straight forward any deployment and changes are to control is an aspect which requires analysis. While SD WAN is simplifying security, your IT team must consider the level of internal knowledge.

8. Will we be able to leverage WAN optimisation?

Certain vendors and providers incorporate advanced application optimisation within their solution capability. SD WAN is, by default, capable of sensing application performance across best path selection, latency and jitter degradation. In certain cases, other features are available including TCP acknowledgement, caching, deduplication and compression.

9. How is traffic handling supported, i.e. load balancing per session or per packet?

The way in which traffic is handled is largely dependant on the available connectivity. If your connectivity is based on dual Ethernet with limited latency and jitter variation, per-packet load balancing is a good way to ensure your business is maximising spend. Where Ethernet and less predictable connectivity is deployed, per-session load balancing is often the preferred option to limit the latency variation between each packet.

10. Does the SD WAN solution support Cloud-based App path selection?

An often discussed SD WAN feature is the ability to use cloud-based apps path selection to ensure the most suitable connection is utilised depending on the application. In some cases, SaaS Cloud services which are Internet-based maybe better accessed via your ISP connection rather than being routed by a private MPLS circuit (as an example). In addition, software WAN will monitor the connection parameters across packet loss, latency and jitter and will adjust the path as required.

11. Will your capability fail to wire in the event of a serious outage?

If any hardware suffers a major outage, how your SD WAN deployment responds is critical. There is the possibility to pass traffic through in the event the device is totally down or suffers poor latency / packet loss.

12. Do you require 3G, 4G, 5G or LTE support for remote users, failover to small branch offices?

5G will provide significant bandwidth and flexibility over the coming years. But even today, 4G/LTE is offering in excess of 100Mbps download bandwidth in some cases. Where small offices and remote users are concerned, wireless connectivity is a great way to support users as SD WAN offers the capability to make the most of bandwidth and traffic routing.

13. How scalable is the solution in terms of end points?

As your SD WAN solution investigation progresses, you will need to understand how scalable your solution is longer term. If your business is small to medium, how scalable the software provider or vendor is will not matter too much. However, for the larger Global Enterprise, scalability is of critical importance.

14. How much bandwidth is the SD WAN device or instance able to support?

The typical bandwidth surrounds symmetrical 100Mbps or 1Gbps Ethernet and everything in-between. If your organisation demands greater bandwidth, e.g. 10Gbps, your IT team will need to understand the maximum throughput of devices.

15. How is the solution licensed from a price / cost perspective?

Setting budgets requires analysing hardware costs, licences and underlying bandwidth associated with your telecoms provider. As mentioned earlier, some SD WAN providers own their own infrastructure with dedicated PoPs and interconnecting bandwidth. In other cases, your business may select a Vendor (such as Meraki) and proceed to procure your own connectivity.

16. Overall, what is the difference between each solution your business is evaluating?

Lastly, once you have identified suitable SD WAN solutions, there will be a need to compare and contrast. Access our Netify portal to easily compare possible providers and vendors to engage, request reports and even consider budgetary pricing.

Conclusion

I hope you've found this article useful, please join in the conversation and leave some comments with any questions below.

Robert is the Managing Director of Netify, a Network Union brand. With experience working across WAN services since 1998, Robert brings a wealth of experience based on hard won knowledge. A writer for Techtarget.com and an experienced business strategist, Robert can bring a tonne of value to your project.